In a steam supply passage to a steam turbine, a steam control valve capable of adjusting the steam supply amount and a steam stop valve capable of stopping supply of steam are disposed.
For instance, Patent Document 1 discloses a steam valve having a stop valve body and a control valve body, whereby the single steam valve has the two functions of a steam stop valve and a steam control valve by itself. Thus, in a case where the steam valve disclosed in Patent Document 1 is used, it is possible to reduce pressure loss as compared to a case in which a steam stop valve and a steam control valve are provided separately.